Overlapping generations can promote altruistic behavior

We use an inclusive fitness model to study the evolution of altruism in a p atch-structured population in which there is positive probability of breede r survival from one generation to the next. We find first that breeder surv ival promotes altruism and second that there is a marked difference between benefits of fecundity and benefits of survival. Under the first altruism i s more strongly favored, and under the second altruism is less strongly fav ored than in a randomly mixing population.